Quantum magnets featured by macroscopic quantum entanglements host exotic quasiparticles and topological order [1]}, [2]}, [3]}. In frustrated spin systems, a valence bond order state with translational symmetry breaking competes with the magnetic order and quantum spin liquid states [4]}, [5]}, [6]}, [7]}. The phase transition between magnetic order and valence bond crystal phases may occur through continuous quantum phase transition [3]}, [9]}, instead of the first-order transition that separates the two phases having competing order parameters in Landau-Ginzburg-Wilson paradigm. The realization of deconfined quantum criticality with fractional excitation has been a fundamental issue of many-body quantum physics [4]}, [11]}, [12]}, [13]}.
